The expression is .

Place value chart for 97 and 28.

Line up the decimal points and draw a line below the numbers.

First find the difference of the ones digit.

Notice that it is not possible to subtract 7 ones from 8 ones.

So, 1 unit must be borrowed from tens column.

The difference of the ones digit = .

Next find the difference of the tens digit.

The difference of the tens digit = .

The difference is .